title: Intraoperative nerve monitoring can reduce prevalence of recurrent laryngeal nerve injury in thyroid reoperations: results of a retrospective cohort study.
abstract: BACKGROUND
  The prevalence of recurrent laryngeal nerve (RLN) injury is higher in repeat than in primary thyroid operations. The use of intraoperative nerve monitoring (IONM) as an aid in dissection of the scar tissue is believed to minimize the risk of nerve injury. The aim of this study was to examine whether the use of IONM in thyroid reoperations can reduce the prevalence of RLN injury.
  
  
  METHODS
  This was a retrospective cohort study of patients who underwent thyroid reoperations with IONM versus with RLN visualization, but without IONM. The database of thyroid surgery was searched for eligible patients (treated in the years 1993-2012). The primary outcomes were transient and permanent RLN injury. Laryngoscopy was used to evaluate and follow RLN injury.
  
  
  RESULTS
  The study group comprised 854 patients (139 men, 715 women) operated for recurrent goiter (n = 576), recurrent hyperthyroidism (n = 36), completion thyroidectomy for cancer (n = 194) or recurrent thyroid cancer (n = 48), including 472 bilateral and 382 unilateral reoperations; 1,326 nerves at risk (NAR). A group of 306 patients (500 NAR) underwent reoperations with IONM and 548 patients (826 NAR) had reoperations with RLN visualization, but without IONM. Transient and permanent RLN injuries were found respectively in 13 (2.6 %) and seven (1.4 %) nerves with IONM versus 52 (6.3 %) and 20 (2.4 %) nerves without IONM (p = 0.003 and p = 0.202, respectively).
  
  
  CONCLUSIONS
  IONM decreased the incidence of transient RLN paresis in repeat thyroid operations compared with nerve visualization alone. The prevalence of permanent RLN injury tended to be lower in thyroid reoperations with IONM, but statistical validation of the observed differences requires a sample size of 920 NAR per arm.
authors.affiliation: Department of Endocrine Surgery, Third Chair of General Surgery, Jagiellonian University Medical College, 37 Prądnicka Street, 31-202, Kraków, Poland, marbar@mp.pl.
authors.forename: Marcin
authors.initials: M
authors.lastname: Barczyński
authors.forename: Aleksander
authors.initials: A
authors.lastname: Konturek
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Pragacz
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Papier
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Stopa
authors.forename: Wojciech
authors.initials: W
authors.lastname: Nowak
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D015994:Incidence; D007431:Intraoperative Complications / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D015995:Prevalence; D061226:Recurrent Laryngeal Nerve Injuries / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control*; D012086:Reoperation; D012189:Retrospective Studies; D013959:Thyroid Diseases / Q000601:surgery*; D013965:Thyroidectomy / Q000009:adverse effects*